NGC 321 is a star cluster that is visible from Earth, in the space of the Cetus constellation. Within the Milky Way Galaxy, the star system of Eminiar is associated with the stars of this grouping, although some of this group has been determined to be much further away, forming another galaxy. (TOS episode: "A Taste of Armageddon")

Stars, systems and objects of the Cetus constellation
13 Ceti • Ceti Alpha (Menkar) • Chi Ceti A • Deneb Kaitos (Beta-16 Ceti) • Gamma Ceti • Epsilon Ceti (Risa) • Mu Ceti (Niburon) • NGC 321 • Omicron Ceti (Mira) • Sigma Ceti • Tau Ceti (Kaferia)

The modern science of astronomy has determined that NGC 321, as viewed from Earth, is made up of a galaxy outside of our own. Since the Enterprise didn't leave our galaxy to access Eminiar, it seems that some stars in our own galaxy are in a line-of sight between that galaxy and Earth when this grouping is referred to.